A painful symptom of dentinal hypersensitivity is caused by a tissue fluid flow change in a dentinal tubule due to a physical stimulus of teeth grinding, brushing, or the like, a stimulus with cold water, etc. It is considered that this symptom is caused when an enamel for blocking the external stimulus is peeled off or a gum is lowered due to a periodontal disease or advancing age, whereby a dentin is exposed and the stimulus is transmitted directly to a dental pulp through the dentinal tubule.
Therefore, in several known methods, the dentinal tubule is physically protected to prevent the transmission of the stimulus to the dental pulp. For example, a method containing forming a polymer membrane on the exposed dentin surface to reduce the dentinal hypersensitivity, a method containing forming a hard coating of an adhesive resin, and the like have been known. However, only qualified dentists can perform these methods. General consumers cannot utilize the methods routinely.
In a known method that general consumers can utilize routinely, an oral composition containing aluminum lactate for protecting the dentinal tubule or potassium nitrate for reducing a sensitivity of a dental pulp cell is used to reduce the dentinal hypersensitivity.
However, the aluminum lactate and potassium nitrate each have an inherent bitter, astringent, or harsh taste. Patent Literature 1 discloses a method for reducing the unpleasant taste.
In addition, the potassium nitrate is disadvantageously less soluble in the case of using the potassium nitrate in combination with sodium lauryl sulfate. Patent Literature 2 discloses a technology for preventing precipitation of the potassium nitrate at low temperature.
Furthermore, Patent Literature 3 discloses a phosphorylcholine-containing polymer usable in an oral composition, and Patent Literature 4 discloses a method using the phosphorylcholine-containing polymer in the oral composition to prevent microbial adhesion in an oral cavity.
Patent Literature 5 discloses usefulness of the phosphorylcholine-containing polymer in dentistry. Specifically, Patent Literature 5 describes a technology for preventing adhesion of a microorganism such as a mold or fungus to a tooth surface.
Patent Literature 6 discloses that the phosphorylcholine-containing polymer can be used in a hypersensitivity-reducing agent in the dental material field. Specifically, Patent Literature 6 discloses a dental composition containing the phosphorylcholine-containing polymer as a tooth surface coating agent.